Backwards-compatible narrowband physical random access channel (NPRACH) for extended range

Abstract

An example method in a wireless device operating in a wireless network comprises generating a random access preamble signal and transmitting the random access preamble signal. The generated random access preamble signal comprises a random access symbol group that comprises a plurality of consecutive symbols, where each of the plurality of consecutive symbols being modulated on a corresponding subcarrier frequency and each of the plurality of consecutive symbols corresponding to a truncated sinusoid of 3.75/N kHz, with N>1.

What is claimed is: 
     
       1. A method, in a wireless device operating in a wireless network, the method comprising:
 generating a random access preamble signal; and 
 transmitting the random access preamble signal; 
 wherein the generated random access preamble signal comprises a random access symbol group that consists of 6/N consecutive symbols, 6/N being an integer greater than or equal to two, each of the consecutive symbols of the random access symbol being modulated on a corresponding subcarrier frequency and each of the consecutive symbols of the random access symbol group corresponding to a truncated sinusoid of 3.75/N KHz, with N>1. 
 
     
     
       2. The method of  claim 1 , wherein the consecutive symbols of the random access symbol group are all modulated on a single subcarrier frequency. 
     
     
       3. The method of  claim 1 , wherein one or more of the consecutive symbols of the random access symbol group are modulated on a first subcarrier frequency and one or more others of the consecutive symbols of the random access symbol group are modulated on a second subcarrier frequency, differing from the first subcarrier frequency. 
     
     
       4. The method of  claim 3 , wherein each of the consecutive symbols of the random access symbol group is modulated on a different subcarrier frequency than all others of the consecutive symbols of the random access symbol group. 
     
     
       5. The method of  claim 4 , wherein each of all but a first one of the consecutive symbols of the random access symbol group is modulated on a subcarrier frequency that is offset by a predetermined number of subcarrier spacings from the subcarrier frequency for the preceding one of the consecutive symbols of the random access symbol group. 
     
     
       6. The method of  claim 4 , wherein a mapping of the consecutive symbols of the random access symbol group to subcarrier frequencies is determined by a hopping matrix, wherein said hopping matrix defines multiple mapping patterns that each depend on a subcarrier frequency for a first one of the consecutive symbols of the random access symbol group. 
     
     
       7. The method of  claim 6 , wherein the hopping matrix is defined such that any random access symbol group defined by the hopping matrix is adjacent to any other random access symbol group defined by the hopping matrix for no more than one symbol time. 
     
     
       8. The method of  claim 6 , wherein the hopping matrix comprises a horizontal axis that corresponds to symbols and a vertical axis that corresponds to subcarrier frequencies, wherein each of a plurality of intra-group hopping patterns is identified in the hopping matrix by a given value that is the same among random access symbols of the same intra-group hopping pattern, and wherein each intra-group hopping pattern has a different value. 
     
     
       9. The method of  claim 1 , wherein the method further comprises receiving, from the wireless network, an indication of N. 
     
     
       10. The method of  claim 1 , wherein the generated random access preamble signal further comprises one or more repetitions of the random access symbol group. 
     
     
       11. A wireless device comprising:
 a radio transceiver configured to communicate with a wireless network; and 
 one or more processing circuits operatively coupled to the radio transceiver and configured to:
 generate a random access preamble signal; and 
 transmit the random access preamble signal, via the radio transceiver; 
 wherein the generated random access preamble signal comprises a random access symbol group that consists of 6/N consecutive symbols, 6/N being an integer greater than or equal to two, each of the consecutive symbols of the random access symbol being modulated on a corresponding subcarrier frequency and each of the consecutive symbols of the random access symbol group corresponding to a truncated sinusoid of 3.75/N kHz, with N>1. 
 
 
     
     
       12. A method, in a wireless access node operating in a wireless network, the method comprising:
 receiving a radio frequency signal; and 
 detecting a random access preamble signal in the received radio frequency signal; 
 wherein the detected random access preamble signal comprises a random access symbol group that comprises a random access symbol group that consists of 6/N consecutive symbols, 6/N being an integer greater than or equal to two, each of the consecutive symbols of the random access symbol being modulated on a corresponding subcarrier frequency and each of the consecutive symbols of the random access symbol group corresponding to a truncated sinusoid of 3.75/N kHz, with N>1. 
 
     
     
       13. The method of  claim 12 , wherein the consecutive symbols of the random access symbol group are all modulated on a single subcarrier frequency. 
     
     
       14. The method of  claim 12 , wherein one or more of the consecutive symbols of the random access symbol group are modulated on a first subcarrier frequency and one or more others of the consecutive symbols of the random access symbol group are modulated on a second subcarrier frequency, differing from the first subcarrier frequency. 
     
     
       15. The method of  claim 14 , wherein each of the consecutive symbols of the random access symbol group is modulated on a different subcarrier frequency than all others of the consecutive symbols of the random access symbol group. 
     
     
       16. The method of  claim 12 , wherein a mapping of the consecutive symbols of the random access symbol group to subcarrier frequencies is determined by a hopping matrix, wherein said hopping matrix defines multiple mapping patterns that each depend on a subcarrier frequency for a first one of the consecutive symbols of the random access symbol group. 
     
     
       17. The method of  claim 16 , wherein the hopping matrix is defined such that any random access symbol group defined by the hopping matrix is adjacent to any other random access symbol group defined by the hopping matrix for no more than one symbol time. 
     
     
       18. A wireless access node comprising:
 a radio transceiver configured to communicate with one or more wireless devices; and 
 one or more processing circuits operatively coupled to the radio transceiver and configured to:
 receive a radio frequency signal; and 
 detect a random access preamble signal in the received radio frequency signal; 
 wherein the detected random access preamble signal comprises a random access symbol group that consists of 6/N consecutive symbols, 6/N being an integer greater than or equal to two, each of the consecutive symbols of the random access symbol being modulated on a corresponding subcarrier frequency and each of the consecutive symbols of the random access symbol group corresponding to a truncated sinusoid of 3.75/N kHz, with N>1.